When we hear about monsoons, we often think about the rainy phase of a season usually occurring in tropical climates. Even though monsoons are associated with much more than just rainfall, as global warming occurs, these complex systems will have several repercussions for precipitation.

ADVERTISEMENT

For example, with warming air, there is potential for a higher holding capacity for rain. In addition, any cooling in the higher atmosphere can change current air pressures thus affecting rainfall patterns.

This has consequences of increased flooding, implications to national water supply, and a potential loss of agricultural productivity due to crop failure for countries across the globe.

In a new study published by scientists at the Potsdam Institute for Climate Impact Research, climate models consistently project significant increases in day-to-day rainfall variability under unmitigated climate change.

Focusing on monsoons in India, researchers conducted computer simulations with a comprehensive set of 20 state-of-the-art climate models and found that Indian monsoon daily variability might increase.

"Increased variability ... translates into potentially severe impacts on people who cannot afford additional loss," says Anders Levermann, one of the study's authors and co-chair of PIK's research domain Sustainable Solutions. "The fact that all these different models agree is a clear message that adaptation measures can be built on." Even if seasonal mean precipitation would remain unchanged, impacts could be substantial, Levermann points out. "Focusing on the average is not always useful. If rainfall comes in a spell and is followed by a drought, this can be devastating even if the average is normal. This requires the right kind of adaptation measures that account for this variability — such as intelligent insurance schemes, for example."

The research found that a 2 degrees Celsius increase in temperature could bear the risk of additional day-to-day variability between 8 and 24 percent above the pre-industrial level. "So limiting global warming is key to reduce day-to-day monsoon variability, adaptation cannot replace but rather complement it," says Levermann.

"This is not about exact percentages. It is the clear trend that conveys the message," says Arathy Menon, lead-author of the study.

However, the consistent result from the models indicate that 4 to 12 percent variability change of daily monsoon rainfall in India are to be expected per degree Celsius of warming. "This is a robust indicator," says Menon.